"Service Engine Soon" Light Inoperative
When engine is started, the ECM grounds terminal "A10" to turn off the "SERVICE ENGINE SOON" light. When ALDL terminal "B" is grounded, it alternately grounds and opens ECM terminal "A10" to flash a code.
NOTE:
Test numbers refer to test numbers on diagnostic chart.
- This test checks for an open ECM fuse or an open in the "SERVICE ENGINE SOON" light circuit, including instrument panel connector, printed circuit and "SERVICE ENGINE SOON" light. Normal response is light on.
- This test checks for a shorted ECM. Grounded ECM terminal "A10" will turn the "SERVICE ENGINE SOON" light off. If disconnecting ECM turns light on, ECM is shorted. Normal response is light on.
- This test checks for a grounded circuit No. 487 from terminal "C" of remote lamp driver to ECM terminal "A10". It also checks for an open circuit No. 439 to terminal "B" of remote lamp driver, a bad ground, or a faulty remote lamp driver. A normal reading is 9-11 volts, because of the voltage drop through the upper resistor in the remote lamp driver. A reading of over 11 volts indicates there is no voltage drop in the remote lamp driver. This indicates a bad ground or faulty remote lamp driver.
- This test checks for an open wire to terminal "B" of remote lamp driver. Normal reading should be close to battery voltage.
- This test checks for a grounded circuit No. 487 from terminal "C" of remote lamp driver to ECM terminal "A10". Normal response is light on.